Principle of starting capacitor , run capacitor . The single-phase current flowing through the single-phase motor can not generate the rotating magnetic field, so the capacitor needs to be used for phase separation, in order to make the current in the two windings produce a phase difference of nearly 90 degree to generate the rotating magnetic field.

Capacitive induction motor has two windings, starting winding and running winding. The two windings differ by 90 degrees in space. A capacitor with large capacity is connected in series on the starting winding. When the operating winding and starting winding pass through single-phase AC, the current in the starting winding is 90 degrees ahead of the current of the operating winding and reaches the maximum value first due to the action of the capacitor. Two identical pulse magnetic fields are formed in time and space, so that a rotating magnetic field is generated in the air gap between the stator and the rotor. Under the action of the rotating magnetic field, the induced current is generated in the motor rotor, and the current interacts with the rotating magnetic field to generate electromagnetic field torque to rotate the motor, Testing Motor Capacitors.

Starting Capacitance

To make the single-phase motor rotate automatically, a starting winding can be added to the stator. The space difference between the starting winding and the main winding is 90 degrees. The starting winding should be connected with a suitable capacitor in series to make the phase difference between the current and the main winding approximately 90 degrees, that is, the so-called phase separation principle. In this way, two currents with a time difference of 90 degrees are connected to two windings with a space difference of 90 degrees, which will produce a (two-phase) rotating magnetic field in space.

Under the action of this rotating magnetic field, the rotor can start automatically. After starting, when the speed rises to a certain value, the starting winding is disconnected with the help of a centrifugal switch or other automatic control device installed on the rotor. Only the main winding works during normal operation. Therefore, the starting winding can be made into a short-time working mode. However, there are many times when the starting winding is continuously opened. This motor is called capacitive single-phase motor. To change the direction of this motor, it can be realized by changing the position of capacitor series connection.